v THE BLOOD: PLASMA 147 



normal, but perfectly obey the same laws that govern the osmotic 

 relations of normal blood-corpuscles. 



In a series of experiments which Manca undertook with the 

 haematocrite method, using solutions of NaCl, KC1, LiCl, he 

 confirmed the previous results obtained with the colori metric, or 

 Hamburger's method, even when the blood had been preserved for 

 two or three months, with or without aseptic measures, or even 

 after saturation with CO. From an average of seven experiments 

 with the haematocrite, undertaken to determine the degree of 

 concentration of NaCl isotonic with the serum and erythrocytes of 

 fresh defibrinated ox blood, he found that it corresponded with a 

 value of 0'82 per cent, a figure somewhat lower than that deter- 

 mined by the cryoscopic estimations of Winter, Fano, and 

 Bottazzi. 



From the sum of Manca's results, it seems legitimate to con- 

 clude that the so-called phenomena of resistance of the erythrocytes 

 (at any rate of those that are non-nucleated) and their osmotic 

 properties, are independent of their vitality, and that the red 

 corpuscles behave like simple, inorganic, artificial Traube's cells, 

 which consist of semi-permeable membranes. 



The above are the most interesting results obtained by the 

 experimental analysis of the osmotic properties of the plasma and 

 blood -corpuscles. From these few indications it would appear 

 that we cannot as yet form a definite physiological opinion on this 

 important subject ; it did not, however, seem proper to omit the 

 matter completely, since it must obviously be of cardinal importance 

 in a not distant future. 



Three methods in particular are to be recommended for the determina- 

 tion of the osmotic pressure of blood-serum and erythrocytes that of Ham- 

 burger, founded on the resistance of the erythrocytes ; the cryoscopic, or 

 Raoult's method, founded on the lowering of the freezing-point ; and that of 

 Hedin and Koppe, founded on the determination of the volume of the 

 erythrocytes by means of the haematocrite. 



Hamburyer'* method for determining the osmotic pressure of blood serum 

 is based on the examination of that solution of NaCl with which it is 

 isotonic. The erythrocytes of mammalia will only part with their haemo- 

 globin when the serum in which they are immersed is diluted with 50-60 per 

 cent distilled water. Thus, to find the value of the solution which gives the 

 exact osmotic pressure, it is only necessary to prepare some specimens of the 

 serum diluted to the required extent. Take six numbered test-tubes, 5 c,c. of 

 serum being added to each. To the first add 3'1 c.c. distilled water, to the 

 second 3 c.c., to the third 2*9 c.c., to the fourth 2'8 c.c., to the fifth 2'7 c.c., and 

 to the sixth 2*6 c,c. Then let three drops of defibrinated blood fall into each 

 test-tube, agitate the mixtures and centrifuge. 



It is known experimentally that the NaCl solution isotonic with 

 mammalian blood, thus diluted, fluctuates between 0*55 and 0'65 per cent. 

 Pour about 8 c.c. of the following solutions of NaCl into six more test-tubes 

 similarly numbered 0'62, 0'61, 0'60, 0'59, 0-58, and 0'57 per cent. Then, as 

 in the first series, let three drops of defibrinated blood fall into each tube, 

 .and shake. 



After two hours the erythrocytes will have sunk to the bottom in all the 



VOL. I La 



